The present invention can be applied to the treatment and diagnosis of a variety of different diseases and abnormalities. Although the present invention is not limited to such, it can be used in the treatment of cancer, wound healing, and a variety of chronic inflammatory diseases. In general, each is presently treated directly by physical means such as surgical removal of cancerous tissue, suturing of wounds and surgical removal of inflamed joints. Further, each can be treated by chemical means. Chemotherapy is applied to cancers, growth hormones are applied to wound healing and anti-inflammatory drugs are applied to treating chronic inflammatory conditions. These, and related treatments are directed, in general, to treating the cancerous, injured, or inflamed tissue directly. In order to provide an understanding on how the present invention departs from conventional treatment modalities a brief and general description of current treatment technologies in these areas is provided.
Cancer Treatments
The term “cancer” encompasses a spectrum of diseases that vary in treatment, prognosis, and curability. The approach to diagnosis and treatment depends on the site of tumor origin, the extent of spread, sites of involvement, the physiologic state of the patient, and prognosis. Once diagnosed, the tumor is usually “staged,” a process which involves using the techniques of surgery, physical examination, histopathology, imaging, and laboratory evaluation to define the extent of disease and to divide the cancer patient population into groups in order of decreasing probability of cure. Such systems are used both to plan treatment and determine the prognoses for the patient (Stockdale (1996) “Principles of Cancer Patient Management,” In: Scientific American Medicine, vol. 3, Dale, D. C., and Federman, D. D. (eds.), Scientific American Press, New York). The type or stage of the cancer can determine which of the three general types of treatment will be used: surgery, radiation therapy, and chemotherapy. An aggressive, combined modality treatment plan can also be chosen. To this end, surgery can be used to remove the primary tumor, and the remaining cells are treated with radiation therapy or chemotherapy. Rosenberg (1985) New Engl. J. Med. 312:1512–14.
Surgery plays the central role in the diagnosis and treatment of cancer. In general, a surgical approach is required for biopsy, and surgery can be the definitive treatment for most patients with cancer. Surgery is also used to reduce tumor mass, to resect metastases, to resolve medical emergencies, to palliate and rehabilitate. Although the primary surgical technique for cancer treatment has involved the development of an operative field where tumors are resected under direct visualization, current techniques allow for some resections to be performed by endoscopic means. A primary concern in the treatment of cancer is the consideration of operative risk (Stockdale, F., supra).
Radiation therapy plays an important role in both the primary and palliative treatment of cancer. Both teletherapy (megavoltage radiation therapy) and brachytherapy (interstitial and intracavity radiation) are in common use. Electromagnetic radiation in the form of x-rays is most commonly used in teletherapy to treat common malignant tumors, while gamma rays, a form of electromagnetic radiation similar to x-rays but emitted by radioactive isotopes of radium, cobalt, and other elements, are also used. Radiation therapy transfers energy to tissues as discrete packets of energy, called photons, that damage both malignant and normal tissues by producing ionization within cells. The target for the ions is most commonly the DNA; radiation therapy exploits the fact that the radiation damage is not uniform between malignant and non-malignant tissues—rapidly dividing cells are more sensitive to DNA damage than quiescent cells (Pass (1993) J. Natl. Cancer Instit. 85:443–56.) Radiation therapy is associated with unique benefits as well as important toxicities. Radiation is preferred in certain anatomic areas, (e.g., the mediastinum), where radiation may be the only feasible local method of treatment, and radiation may also be the only feasible local modality if tumor involvement is extensive. Radiation may also be used when the patient finds surgery unacceptable, or when the patient's medical condition prohibits a surgical procedure. Radiation treatment involves tissue damage which can lead to early and late radiation effects. The early effects (acute toxicity of radiation therapy) include erythema of the skin, desquamation, esophagitis, nausea, alopecia, and myelosuppression, while the late effects include tissue necrosis and fibrosis, and usually determine the limiting toxicity of radiation therapy (Stockdale, F., supra).
Nearly all chemotherapeutic agents currently in use interfere with DNA synthesis, with the provision of precursors for DNA and RNA synthesis, or with mitosis, and thus target proliferating cells (Stockdale, F., “Cancer growth and chemotherapy,” supra). Animal tumor investigation and human clinical trials have shown that drug combinations produce higher rates of objective response and longer survival than single agents (Frei (1972) Cancer Res. 32:2593–2607). Combination drug therapy uses the different mechanisms of action and cytotoxic potentials of multiple drugs, including the alkylating agents, antimetabolites, and antibiotics (Devita, et al. (1975) Cancer 35:98–110). The physiologic condition of the patient, the growth characteristics of the tumor, the heterogeneity of the tumor cell population, and the multidrug resistance status of the tumor influence the efficacy of chemotherapy. Generally, chemotherapy is not targeted (although these techniques are being developed, e.g. Pastan (1986) Cell 47:641–648), and side effects such as bone marrow depression, gastroenteritis, nausea, alopecia, liver or lung damage, or sterility can result.
Wound Healing
Wound healing is a complex and protracted process of tissue repair and remodeling involving many different cell types which requires a finely tuned control of various biochemical reaction cascades to balance the regenerative processes. Wound healing is generally divided into three phases: inflammation, proliferation, and maturation (Waldorf, et al. (1995) Adv. Dermatol. 10:77–96). The process comprises the migration of different cell types into the wound region, growth stimulation of epithelial cells and fibroblasts, formation of new blood vessels, and the generation of extracellular matrix. The correct functioning of these processes depends on the biological activation of various cytokines (Bennett, et al. (1993) Am. J. Surg. 165:728–37). Nutrition, the immune system, oxygen, blood volume, infection, immunosuppression, and a decrease in red blood cells are all influential factors in wound healing (Witney, (1989) Heart Lung 18: 466–474).
The quality as well as the rate of wound healing is usually dependent on the type and extent of the original injury. Three general types of process are used to treat wounds, each of which is directed to healing the damaged tissue. Closure of wounds is most commonly accomplished by suturing, although tapes, stapling or electrocautery can also be used (Wheeless, C. R., 1996, Wheeless' Textbook of Orthopaedics) (Garrett, et al. (1984) J. Hand. Surg. 9(5):683–92). Skin tapes and various sutures each exhibit certain benefits and disadvantages in primary closure of wounds. Skin tapes cause less inflammatory reaction but fail to close the subepithelial wound spaces, while the inflammatory reaction and subsequent scarring caused by various sutures depends upon the size of the suture needle, the diameter of the suture material, and whether it is a monofilament or woven suture (Simpson, (1977) Laryngoscope 87: 792–816).
In a wound, the size of an inoculum of microorganisms, the virulence of the organisms, and host antimicrobial defense mechanisms determine if an infection will develop. Thus, antibiotics can also be of therapeutic value in the treatment of wounds (Edlich, (1986) Emergency Medical Clinics of North America 4(3):561–80). The pharmacological action of each antibiotic must be understood in order to choose the proper antibiotic, its route of administration, and to avoid side effects (Simpson, supra). Recent results suggest that antibiotic therapy allows cell proliferation and differentiation to proceed more rapidly and thus may be helpful in augmenting wound repair (Barrow, et al. (1994) Respiration 61:231–5; Maeder, et al. (1993) Paraplegia 31: 639–44). Proteolytic enzymes have also been used as adjuncts to antibiotic treatment of contaminated wounds (Rodeheaver, et al. (1978) Am. J. Surg. 136(3):379–82).
The topical administration of various cytokines, including bFGF, EGF, PDGF, and TGF-beta, either alone or in combination, may considerably accelerate wound healing (Moulin, (1995) Eur. J. Cell. Biol. 68:1–7). Growth factors attract cells into the wound, stimulate their proliferation, and have profound influence on extracellular matrix deposition. Since developing the ability to mass-produce these cytokines by recombinant techniques, many studies have demonstrated that growth factors can augment all aspects of tissue repair in normal and impaired healing models (e.g., Schultz, et al. (1987) Science 235: 350–2; Deuel, et al. (1991) Annu. Rev. Med. 42: 567–84). Although preliminary clinical trials have shown that growth factor treatment has occasionally led to statistically significant improvements in tissue repair, it is not clear that these results are clinically significant, and it has been suggested that new clinical trials must focus on targeting growth factors for specific types of impaired healing (Greenhalgh, (1996) J. Trauma 41:159–67).
Chronic Inflammation
Natural, humoral, and cellular immune mechanisms have all been implicated in the pathogenesis of chronic inflammatory diseases (Seymour, et al. (1979) J. Oral Pathol. 8:249–65). Autoimmune diseases result from abnormalities in lymphocyte function. Abnormalities in T cell function can be responsible for disease through cell-mediated immunity, and the activity of helper T cells in the production of antibodies may contribute to autoantibody formation. The central role of helper T cells in autoimmune disease is supported by the association of many of these diseases with certain HLA molecules. The failure of one or more steps in the maintenance of tolerance could result in autoimmunity (Robinson (1996) “Immunologic Tolerance and Autoimmunity,” in: Scientific American Medicine, Vol. 2, Section VI, Scientific American Press, New York, p. 1–11).
Several types of treatment are used in autoimmune disease, all of which are directed at lessening the immune response in the affected tissue. For example, treatment for rheumatoid arthritis, an autoimmune disease, can utilize anti-inflammatory agents such as nonsteroidal anti-inflammatory agents (NSAIDs) or glucocorticosteroids, remission inducing agents such as gold salts, and/or immunosuppressive drugs such as cyclophosphamide. Orthopedic surgery can also be used to replace joints damaged during the inflammatory process (see Gilliland, B. C., and Mannik, M., 1983, “Rheumatoid Arthritis” In: Harrison's Principles of Internal Medicine, McGraw Hill, New York, P. 1977–1984). Recent work has suggested the possibilities of new treatments, also directed to the affected tissue, such as the use of TNFα in the treatment of rheumatoid arthritis (Brennan, et al. (1995) Br. Med. Bull. 51:368–384).
Allergy refers to a condition in which the immune response to environmental antigens causes tissue inflammation and organ dysfunction. As in the autoimmune diseases, the data suggest an interaction of several components of the immune system in allergic diseases. The diversity of expression of allergic diseases arises from different immunologic effector mechanisms, which evoke specific patterns of tissue injury (Beer, et al. (1996) “Allergy,” In: Scientific American Medicine, Vol. 2, Section VII, Scientific American Press, New York, P. 1–29). The clinical features of each allergic disease reflect the immunologically mediated inflammatory response in the affected organs or tissues (e.g. asthma reflects an inflammatory response in the airways).
Several treatment strategies are used to treat the immune-mediated allergic diseases, all of which are directed at lessening the immune response in the inflamed tissue. For example, in the treatment of asthma, therapy can involve environmental control, pharmacotherapy, and allergen immunotherapy (Beer, et al. (1996) “Allergy,” In: Scientific American Medicine, Vol. 2, Section VII, Scientific American Press, New York, pp. 1–29). In the treatment of asthma, elimination of the causative agent is the most successful means of preventing the inflammation. However, this is often not possible, and thus several classes of drugs have been used. These include the methylxanthines (for bronchodilation), adrenergic stimulants (stimulation of α-adrenergic receptors, bronchodilators), glucocorticoids (lessen inflammation in the lung), chromones (downregulate mast cells, lessen inflammation in the lung), and anticholinergics (bronchodilators) (McFadden, et al., “Lung disease caused by immunologic and environmental injury,” In: Harrison's Principles of Internal Medicine, McGraw Hill, N.Y. p. 1512–1519). Desensitization or immunotherapy with extracts of the suspected allergens has also been suggested in order to reduce inflammation in asthma (McFadden and Austen, op. cit.; Jacquemin and Saint-Remy (1995) Ther. Immunol. 2:41–52).
Atherosclerotic Plaques
Atherosclerosis is the progressive narrowing of the lumen (inner passageway) of arterial blood vessels by layers of plaque (fatty and fibrous tissues). The major complications of atherosclerosis, including ischemic heart disease, myocardial infarction, stroke, and gangrene of the extremities, account for more than half of the annual mortality in the United States.
Arteries are composed of three layers: the intima, which comprises endothelium and connective tissue on the luminal side of the internal elastic lamina; the media, which comprises smooth muscle cells and, in the elastic arteries, elastic fibers, and, in large vessels, the vasa vasorum; and the adventitia, which is the external layer of the vessel wall and comprises a connective tissue sheath composes of fibroblasts, small vessels, and nerves. Atherosclerosis can occur in any artery. In coronary arteries, it may result in heart attacks; in cerebral arteries it may result in strokes; and in peripheral arteries it may result in gangrene of the extremities. Atherosclerosis is a complex process, and precisely how it begins or what causes it is not known. However, endothelial injury is believed to be an initial step in the formation of atherosclerotic lesions, and may be caused by hemodynamic strain, hypercholesterolemia, hypertension or immune complex disease. Endothelial injury leads to cholesterol and lipid accumulation, intimal thickening, smooth muscle cell proliferation, and formation of connective tissue fibers. Gradually, the build-up of fatty deposits and the proliferation of the smooth muscle cells lead to the formation of plaques which eventually narrow and block the artery.
Neovascularization within the intima of human atherosclerotic lesions has been described, but its role in the progression of atherosclerosis is unclear. Moulton, et al. (1999) Circulation 99:1726–1732; Isner (1999) Circulation 99:1653–1655; Depre, et al. (1996) Catheterization and Cardiovascular Diagnosis 39:215–220.
The mortality rate due to atherosclerosis and related pathologies makes it clear that current treatments are inadequate. The factor most important in causing atherosclerotic events is a high blood plasma concentration of cholesterol in the form of low-density lipoproteins. Current methods of treatment include drugs which inhibit the liver enzyme system for cholesterol synthesis.
Current Treatments—Immunology
The treatment regimes described above have had varying degrees of success. Because the success rate is far from perfect in many cases research continues to develop better treatments. One promising area of research relates to affecting the immune system. By the use of genetic engineering and/or chemical stimulation it is possible to modify and/or stimulate immune responses so that the body's own immune system treats the disease e.g., antibodies destroy cancer cells. This type of treatment departs from those described above in that it utilizes a biological process to fight a disease. However, the treatment is still a direct treatment meaning that the antibodies created directly attack the cancer cells.
The present invention can be utilized for treatments which involve a radical departure from normal treatments in that the present invention does not involve directly affecting the cancerous, damaged or inflamed cells.
Others have recognized that, at least theoretically, it is possible to treat cancer or inflammation associated with angiogenesis by inhibiting the angiogenesis. A typical example of the current thinking relating to such is discussed within PCT Publication WO 95/25543, published Sep. 28, 1995. This published application describes inhibiting angiogenesis by administering an antibody which binds to an antigen believed to be present on the surface of angiogenic endothelial cells. Specifically, the application describes administering an antibody which binds to αvβ3 which is a membrane receptor believed to mediate cell-cell and cell-extracellular matrix interactions referred to generally as cell adhesion events. By blocking this receptor the treatment hopes to inhibit angiogenesis and thereby treat cancer and inflammation.